Toll of climate change on world food supply could be worse than thought

Dec 03, 2007

Global agriculture, already predicted to be stressed by climate change in coming decades, could go into steep, unanticipated declines in some regions due to complications that scientists have so far inadequately considered, say three new scientific reports.

The authors say that progressive changes predicted to stem from 1- to 5-degree C temperature rises in coming decades fail to account for seasonal extremes of heat, drought or rain, multiplier effects of spreading diseases or weeds, and other ecological upsets. All are believed more likely in the future. Coauthored by leading researchers from Europe, North America and Australia, they appear in this week’s issue of the Proceedings of the National Academy of Sciences.

“Many people assume that we will never have a problem with food production on a global scale. But there is a strong potential for negative surprises,” said Francesco Tubiello, a physicist and agricultural expert at the NASA/Goddard Institute of Space Studies who coauthored all three papers. Goddard is a member of Columbia University’s Earth Institute.

In order to keep pace with population growth, current production of grain—from which humans derive two-thirds of their protein—will probably have to double, to 4 billion tons a years before 2100. Studies in the past 10 years suggest that mounting levels of carbon dioxide in the air—believed to be the basis of human-caused climate change—may initially bolster the photosynthetic rate of many plants, and, along with new farming techniques, possibly add to some crop yields. Between now and mid-century, higher temperatures in northerly latitudes will probably also expand lands available for farming, and bring longer growing seasons. However, these gains likely will be canceled by agricultural declines in the tropics, where even modest 1- to 2-degree rises are expected to evaporate rainfall and push staple crops over their survival thresholds. Existing research estimates that developing countries may lose 135 million hectares (334 million acres) of prime farm land in the next 50 years. After mid-century, continuing temperature rises—5 degrees C or more by then--are expected to start adversely affecting northern crops as well, tipping the whole world into a danger zone.

The authors of the PNAS studies say that much of the previous work is oversimplified, and as a consequence, the potential for bigger, more rapid problems remains largely unexplored. “The projections show a smooth curve, but a smooth curve has never happened in human history,” said Tubiello. “Things happen suddenly, and then you can’t respond to them.” For instance, extreme-weather events of all kinds, including heat waves or sudden big storms, could easily wipe out crops on vast scales if they occur for even a few days during critical germination or flowering times. Tubiello says this is already happening on smaller scales. During a heat wave in the summer of 2003, temperatures in Italy soared 6 degrees C over their long-term mean, and the corn yield in the rich Po valley dropped a record 36%. Nearly all the world’s pastures are rain-fed; in Africa, droughts in the 1980s and 1990s wiped out 20% to 60% of some nations’ herds. Such events on larger scales could arise with little or no warning in the near future, the authors suggest.

Higher temperatures may also prompt outbreaks of weeds and pests, and affect plant or animal physiology—factors also left out of most projections. One of the new PNAS studies, “Crop and Pasture Response to Climate Change,” says that more recent modeling suggests cattle ticks and bluetongue (a viral disease of sheep and cattle) will move outward from the tropics to areas such as southern Australia. Other new models suggest that higher temperatures will limit the ability of modern dairy-cow breeds to convert feed into milk, and lead to declines in livestock fertility and longevity. As temperatures rise in northerly latitudes, the ability of crop pests to survive winters is expected to improve, enabling them to attack spring crops in regions where they were previously kept at bay during this vulnerable time.

The authors say that farmers may temporarily mitigate some effects of changing climate by moving toward adaptations now. Adaptations already being considered or set up include regional climate-forecasting systems that enable farmers to switch to different crops or change the timing of plantings; introduction of new varieties or species that can withstand anticipated conditions; and improved flood-mitigation and water-storage facilities. One of the PNAS studies, “Adapting Agriculture to Climate Change,” says that such adaptations might help tropical farmers cut damages wrought by rises of 1.5 to 3 degrees, and temperate-region farmers, damages from 1- to 2-degree rises. This would buy a few decades of time for nations to agree on ways to slow or reverse the warming itself. “After that, all the bets are off,” said Tubiello.

Source: The Earth Institute at Columbia University

Explore further: Pact with devil? California farmers use oil firms' water

Related Stories

Reducing agriculture's greenhouse gas emissions

Jun 23, 2015

The overwhelming scientific consensus is that gases produced by human activity are affecting the global climate. But even if you don't believe the current warming of the global climate is caused by humans, it's only common sense that cutting back on h ...

"Weirdo" mutant plant opens doors for food security

Jun 15, 2015

The discovery that an Australian tobacco plant studied internationally as part of plant breeding programs is actually the genetic "weirdo" of its family holds huge potential for food security, experts say.

Recommended for you

Gimmicks and technology: California learns to save water

Jul 03, 2015

Billboards and TV commercials, living room visits, guess-your-water-use booths, and awards for water stinginess—a wealthy swath of Orange County that once had one of the worst records for water conservation ...

Cities, regions call for 'robust' world climate pact

Jul 03, 2015

Thousands of cities, provinces and states from around the world urged national governments on Thursday to deliver a "robust, binding, equitable and universal" planet-saving climate pact in December.

Will climate change put mussels off the menu?

Jul 03, 2015

Climate change models predict that sea temperatures will rise significantly, including in the tropics. In these areas, rainfall is also predicted to increase, reducing the salt concentration of the surface ...

As nations dither, cities pick up climate slack

Jul 02, 2015

Their national governments hamstrung by domestic politics, stretched budgets and diplomatic inertia, many cities and provinces have taken a leading role—driven by necessity—in efforts to arrest galloping ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

NotParker
5 / 5 (1) Dec 03, 2007
Actually, the real porblem is that AGW fanatics have convinced farmers to grow corn to be made into ethanol, thereby removing it from the food supply. That has already made corn a lot more expensive. And anything that eats corn ... such as cattle will also become more expensive.


mikiwud
not rated yet Dec 04, 2007
The real problem will be when temperatures fall.
Another mini ice age whith the world population so much higher than during the last one.......!
Still,all the con merchants can move to Bali and have THEIR food flown in.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.